N = int(input())
A = input()

r_cnt = A.count('R')

ans = 0
for i in range(r_cnt):
    if A[i] != 'R':
        ans += 1

print(ans) N = int(input()) N int(input()) int input() input A = input() A input() input r_cnt = A.count('R') r_cnt A.count('R') A.count A count 'R' ans = 0 ans 0 for i in range(r_cnt):
    if A[i] != 'R':
        ans += 1 i range(r_cnt) range r_cnt if A[i] != 'R':
        ans += 1 A[i] != 'R' A[i] A i 'R' ans += 1 ans 1 print(ans) print ans A = input() input() A ans += 1 1 ans ans = 0 0 ans r_cnt = A.count('R') A.count('R') r_cnt N = int(input()) int(input()) N
N = int(input())
A = input()

r_cnt = A.count('R')

ans = 0
for i in range(r_cnt):
    if A[i] != 'R':
        ans += 1

print(ans)